#include <stdio.h>
#include <iostream>
#define VNAME(name) (#name)
#define debug(x) {int debug_x = x; std::cout << " (" << VNAME(x) << ": " << (debug_x) << ") ";}

int main()
{
    int i, t, n;
    scanf("%d", &n);
    float a, b, s = 0;
    for (b = 1; b <= n; i++)
    {
        for (a = 2; a <= n; a++)
            debugs = s + a / b;
        debug(t = a;
        debug(a = a + b;
        b = t;
    }
    printf("%.2f", s);
    return 0;
}
